Spinal fixation tool attachment structure

ABSTRACT

A tool set for implanting bone screws in a human spine, followed by the implantation of a rod into the bone screws includes end guide tools having flexible back wall flaps that receive opposite ends of the rod and intermediate guide tools that hold the rod in intermediate locations between the end guide tools. Both the end and intermediate guide tools include an attachment structure for operably connecting the guide tool to a bone screw. The attachment structure includes an undercut and/or recess so as to resist splaying and separation of the guide tool from an attached bone screw.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 16/662,826, filed Oct. 24, 2019, which a continuation of U.S. patent application Ser. No. 14/601,834 filed Jan. 21, 2015, now U.S. Pat. No. 10,485,588, which a continuation of U.S. patent application Ser. No. 11/272,508, filed Nov. 10, 2005, which claims the benefit of U.S. provisional patent application Ser. No. 60/630,536, filed Nov. 23, 2004, and which is also a continuation-in-part of U.S. patent application Ser. No. 10/996,289, filed Nov. 23, 2004, now U.S. Pat. No. 8,152,810 and is also a continuation-in-part of U.S. patent application Ser. No. 10/789,149, filed Feb. 27, 2004, now U.S. Pat. No. 7,160,300, each of which are incorporated entirely by reference herein.

BACKGROUND OF THE INVENTION

The present invention relates to apparatuses and methods for use in performing spinal surgery and, in particular, to tools and methods of using such tools, especially for percutaneously implanting spinal screws and for implanting a rod for spinal support and alignment, using minimally invasive techniques.

For many years, spinal osteosynthesis apparatuses have been utilized to correct spinal deformities, injuries or disease. In such procedures, elongate rods are surgically attached to vertebrae of the spine to provide support and/or to realign or reposition certain vertebrae. Such rods are secured to vertebrae utilizing bone screws and other spinal implants. In order to reduce the impact of such surgery on the patient, a desirable approach is to insert such implants percutaneously or with surgical techniques that are minimally invasive to the body of the patient.

Problems arise when implantation tools designed for traditional surgery that is highly invasive are utilized in percutaneous surgery. The tools may be bulky, oversized or have irregular surfaces or protrusions. A projecting actuator arm or fastening member may be useful with respect to the spinal screw implantation process or the rod reduction process, but there is insufficient clearance to use such structure and/or such structure may produce additional invasive trauma which the percutaneous surgery is attempting to avoid.

A percutaneous procedure also presents a problem with implantation of rods that are elongate and have historically required a long incision and open wound in order to provide for the length of the rod and the space required for the surgeon's hands to manipulate the rod. Such problems are then compounded by the implants and insertion tools used with the rod.

Consequently, it is desirable to develop apparatuses and techniques that allow for the insertion of bone screws, the insertion and reduction of a rod into the bone screws and the securing of the rod to the bone screws with significantly less invasion into the body of the patient and with minimal surgical incision of the skin over the operational site.

SUMMARY OF THE INVENTION

A tool assembly and a set of tools according to the invention is provided for percutaneously implanting bone screws and an associated spinal rod in a patient. The tool assembly includes an elongate guide tool with implant engaging members and a multi-purpose installation tool. The multi-purpose tool is a stabilizer for the guide tool implant engaging members which also functions as a rod stabilizer tang container and deployer and a rod pusher and reducer. The guide tool has a lower end configured with opposed implant engaging members for releasable attachment to a spinal implant bone screw, hook, etc. The multi-purpose installation tool is elongate, and preferably includes a translation nut and attached sleeve which has a lower end for engaging and containing the rod stabilizer tang prior to rod insertion and later pushing on the rod for reduction. The translation nut is coaxial and freely rotatable with respect to the sleeve. The nut is configured for rotatable attachment to an upper end of the guide tool. The multi-purpose installation tool sleeve is attachable or securable to the guide tool in a first bone screw implantation orientation and in an alternative second rod pushing orientation. In the first, bone screw implantation orientation, the sleeve is disposed in a fixed, stationary position with respect to the guide tool, with the sleeve substantially surrounding the guide tool and retaining a flexible tang. In the second or rod pushing orientation, the sleeve is slidable along an axis of the guide tool and the nut can be rotated, thereby translating the rod pushing end between a first location substantially spaced from the guide tool end and a second location near the guide tool end for rod reduction.

The tool assembly may further include a driver having a handle, a guide tool attachment portion and a stem, the stem having an end configured for rotatable engagement with a spinal implant screw. The driver is in coaxial relationship with both the guide tool and the multi-purpose installation tool when the stem is disposed within the guide tool with the guide tool attached to the multi-purpose installation tool. The attachment portion of the driver is configured for rigid attachment to the guide tool, preventing rotation of the driver in relation to the guide tool.

A tool set according to the invention includes at least a pair of end guide tools. Each end guide tool includes an elongate body having opposed implant engaging members with lower attachment structure adapted for attachment to a respective bone screw. The body has an inner surface defining an elongate and laterally opening channel. Preferably, the guide tool body further defines an elongate opening communicating with the channel and a back wall with a flexible holding structure, the wall and holding structure disposed opposite the lateral opening. The back wall flexible holding structure includes first and second elongate and parallel slits in the lower back wall portion creating a movable tab or tang disposed between the first and second slits. The flexible flap or tang partially defines the elongate channel. Furthermore, during insertion procedures, the tang may be pushed so as to flex, hinge or spring at an upper end thereof and so that a lower end angulates and translates outwardly or to a location lateral relative to a remainder of the back wall, with the channel adapted to receive a respective rod therein. When an end of the rod is inserted in the lower end channel, the tang may be resiliently flexed further outwardly to accommodate the length of the rod while maintaining, containing and stabilizing the rod in a desired position relative to bone screws.

The multi-purpose installation tool is attachable to the end guide tool in a first, bone screw implantation configuration position and in an opposite second, rod pushing configuration or position. In the first position, an elongate slot or opening in the sleeve of the tool support is aligned with and fixed in adjacent relationship to the channel opening of the end guide tool, with the sleeve of the tool being held adjacent to the back wall portion and retaining the spring tang. In the second, rod pushing position, the end guide tool back wall portion and the tool sleeve opening are fixed in adjacent relationship with the back wall tang portion protrudeable into the tool sleeve opening.

An intermediate guide tool according to the invention includes an end with opposed first and second implant engaging legs defining a longitudinal pass-through opening, passageway or slot for receiving a rod therethrough. When attached to a multi-purpose installation tool in the first, bone screw implantation orientation, the tool sleeve is disposed in a fixed, stationary position substantially surrounding and supporting both the intermediate guide tool legs. In the second or rod pushing orientation, the sleeve is in sliding relation along an axis of the intermediate guide tool, with the sleeve and associated rod pushing end translatable along the first and second legs between a first location spaced from the intermediate guide tool end and a second location adjacent or near the guide tool end.

A vertebral support rod implantation kit according to the invention, adapted for use with a plurality of vertebrae, includes a plurality of polyaxial bone screws, each bone screw being adapted for implantation in one vertebra, each of the bone screws having an attachment structure. It is foreseen that the polyaxial bone screws can be cannulated and/or fixed. The kit also includes an elongate rod having first and second ends, the rod sized and shaped to extend between a pair of end bone screws of the plurality of bone screws, which can be fixed, polyaxial and cannulated or not cannulated. The kit further includes a plurality of closure tops with each closure top being sized and shaped to mate with a respective bone screw and capture or retain the elongate rod within a cavity or channel defined by the respective arms of the bone screw. Additionally, the kit includes a pair of end guide tools, and may include one or more intermediate guide tools, each guide tool being attachable to multi-purpose installation tools, as described herein and bone screw drivers, the drivers being configured to be rigidly attached to a respective end guide tool or intermediate guide tool.

In a method according to the invention, a spinal fixation tool assembly is assembled by first attaching a bone screw head of a spinal implant screw to a mating attachment structure disposed at a first end of an elongate guide tool implant engaging member, the guide tool defining a laterally opening channel and having a second attachment structure disposed at a second end thereof. The guide tool and attached spinal implant screw may then be inserted into a multi-purpose installation tool, the tool having a translation nut, or the like, and a sleeve-like structure. The nut or similar part is rotated or manipulated in a first direction to mate the tool support with the second attachment structure on the guide tool and translate the sleeve or similar surrounding structure to a location near the guide tool first end. Then, a driver is inserted into the guide tool channel, the driver having a handle and a spinal implant screw engagement end. In the illustrated embodiment, the driver is attached to the guide tool at the second attachment structure with the driver engagement end engaging the spinal implant screw. It is foreseen that the guide tool could be attached to the screw and the screw inserted with the driver without the need for additional tools.

A method according to the invention may also include the steps of inserting the attached driver, guide tool and spinal implant screw into an incision, especially a minimally invasive incision sized to snugly or closely receive the assembled tools and bone screw, and into contact with a vertebra, followed by turning the driver handle. By turning the handle, the driver, the associated tools and the spinal implant screw are rotated as one assemblage or unit, driving the spinal implant screw into the vertebra.

Further method steps according to the invention include detaching the drivers from the attached guide tool and multi-purpose installation tool, if used, and withdrawing the drivers from the incisions, followed by detaching the multi-purpose installation tools, if used, from the end guide tools and thereby deploying the end tangs. If used, it may also be desirable to detach the multi-purpose installation tools from the intermediate guide tools, if any.

According to one embodiment of the invention, during rod insertion, a respective multi-purpose installation tool may be utilized for rod reduction and accordingly replaced on each end guide tool with the sleeve opening thereof aligned with the end guide tool flexible wall or tang to allow the tang to remain flexed outward. Then a rod first end may be inserted into an incision through which one of the end guide tools has been inserted, and then guided into a channel of an adjacent end or intermediate guide tool. The rod is then guided into and through all remaining channels with first and second ends of the rod each in contact with a flexible wall or deployed tang of a respective end guide tool with the tangs biasing against the rod ends, and with the rod extending through all associated guide tools. The multi-purpose installation tool sleeve is then utilized as a rod pusher by rotating the nut and sliding the closed end of the sleeve toward the lower guide tool end, the sleeve end contacting the rod and pushing the rod toward the bone screw.

The attachment structure for joining the guide tool to the bone screw includes radial mating projections and receivers or grooves that allow the guide tool to be twisted on and twisted from the head of the bone screw. For example, an external attachment on the bone screw head can have tapered undercut upper surfaces. Additional attachment structures according to the invention include snap-on/twist off, snap-on/pry-off, slide-on/push-off, snap- or slide-on/slide off, and other combinations. It is foreseen that other attachment structure could be used such as clip-on/clip-off, clip-on/twist-off, snap-on/snap-off, spring-on/spring-off, spring-on/twist-off, set screws, etc. The attachment structure secures the guide tool to the bone screw during insertion of the screw into bone, but allows the tool to release from the bone screw for removal of the tool at the end of the procedure by rotation of the tool about a central axis thereof or by some other mechanism, as described herein.

OBJECTS AND ADVANTAGES OF THE INVENTION

Therefore, the objects of the present invention are: to provide a compact tool assembly for supporting and installing bone screws and other implants with minimal surgical invasion to the patient; to provide such an assembly wherein a tool providing support and stabilization for implant engaging members of the assembly during bone screw implantation may also be utilized for deployment of rod containment tangs and as a rod reducer; to further provide a set of tools for implanting a spinal rod for support or alignment along a human spine with minimal surgical invasion of the patient; to provide such a set of tools including a pair of end tool guides for slidably guiding opposed ends of the rod toward end bone screws attached to the end guide tools; to provide such a set of tools including intermediate guide tools for each intermediate bone screw that guide the rod in slots therethrough to respective bone screws; to provide such a set of tools including rod and closure top installation tools for assisting in securing the rod in the bone screws; to provide such a set of tools wherein the guide tools are easily attached to and disengaged from the bone screws; to provide such a set of tools wherein the guide tools, guide tool supports or stabilizers, tang containment and deployment tools, rod reduction tools, bone screw installation tools and closure top installation tools are all easily aligned, positioned, and engaged, if necessary, with respect to the bone screw and are disengaged from the bone screw and other tools in the installation assembly by manual manipulation of the surgeon; to provide a method of implanting a rod into bone screws within a patient with minimal or less surgical invasion of the patient; to provide such a method utilizing the previously described tools for percutaneous implantation of such a rod; and to provide such a set of tools and methods that are easy to use and especially adapted for the intended use thereof and wherein the tools are comparatively inexpensive to produce.

Other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention.

The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded front elevational view of a tool assembly according to the present invention showing a driver tool, a multi-purpose installation tool implant engaging member stabilizer sleeve/tang container and deployer/rod pusher and reducer and an end guide tool shown with an attached polyaxial bone screw.

FIG. 2 is an enlarged front elevational view of an intermediate guide tool of the invention.

FIG. 3 is an enlarged side elevational view of the intermediate guide tool of FIG. 2 .

FIG. 4 is an enlarged rear elevational view of the intermediate guide tool of FIG. 2 .

FIG. 5 is an enlarged front elevational view of the end guide tool of FIG. 1 .

FIG. 6 is an enlarged side elevational view of the end guide tool of FIG. 5 .

FIG. 7 is an enlarged rear elevational view of the end guide tool of FIG. 5 .

FIG. 8 is a cross-sectional view of the end guide tool, taken along the line 8-8 of FIG. 5 .

FIG. 9 is an enlarged cross-sectional view of the intermediate guide tool, taken along the line 9-9 of FIG. 2 .

FIG. 10 is an enlarged cross-sectional view of the intermediate guide tool, taken along the line 10-10 of FIG. 2 .

FIG. 11 is an enlarged bottom plan view of the intermediate guide tool of FIG. 2 .

FIG. 12 is an enlarged and fragmentary perspective view of a polyaxial bone screw of the invention.

FIG. 13 is an enlarged and fragmentary front elevational view of the polyaxial bone screw of FIG. 12 .

FIG. 14 is an enlarged and fragmentary side elevational view of the polyaxial bone screw of FIG. 12 .

FIG. 15 is an enlarged and fragmentary side elevational view of the polyaxial bone screw of FIG. 12 disposed opposite the side shown in FIG. 14 .

FIG. 16 is an enlarged top plan view of the polyaxial bone screw of FIG. 12 .

FIG. 17 is an enlarged and fragmentary front elevational view of the polyaxial bone screw of FIG. 12 and the intermediate guide tool of FIG. 2 , shown at an early stage of a twist-on installation of the intermediate guide tool to the bone screw head.

FIG. 18 is an enlarged and fragmentary cross-sectional view of the intermediate guide tool and polyaxial bone screw installation, taken along the line 18-18 of FIG. 17 .

FIG. 19 is an enlarged and fragmentary cross-sectional view similar to FIG. 18 , showing a later stage of the twist-on installation of the intermediate guide tool to the bone screw head.

FIG. 20 is an enlarged and fragmentary cross-sectional view similar to FIGS. 18 and 19 , showing the intermediate guide tool installed on the bone screw head.

FIG. 21 is an enlarged, fragmentary and cross-sectional view, taken along the line 21-21 of FIG. 20 , showing the intermediate guide tool installed on the bone screw head.

FIG. 22 is an enlarged front elevational view of the multi-purpose tool shown in FIG. 1 .

FIG. 23 is a cross-sectional view of the multi-purpose tool taken along the line 23-23 of FIG. 22 .

FIG. 24 is an enlarged bottom plan view of the multi-purpose tool of FIG. 22 .

FIG. 25 is an enlarged and fragmentary cross-sectional view of a portion of the multi-purpose tool shown in FIG. 23 .

FIG. 26 is an enlarged and fragmentary side elevational view of the driver shown in FIG. 1 having a handle, a nut fastener and a stem, with the nut fastener being shown in a first, unengaged position.

FIG. 27 is an enlarged and fragmentary front elevational view of the driver tool similar to FIG. 26 , showing the nut fastener in a second or intermediate position.

FIG. 28 is an enlarged and fragmentary side elevational view similar to FIG. 27 and further showing a cross-sectional view of the nut fastener, taken along the line 28-28 of FIG. 27 .

FIG. 29 is an enlarged cross-sectional view similar to FIG. 23 , showing an early stage of the installation of the multi-purpose tool to the end guide tool (shown in side elevation as in FIG. 6 ).

FIG. 30 is an enlarged cross-sectional view similar to FIG. 29 , showing the multi-purpose tool installed to the end guide tool (shown in side elevation).

FIG. 31 is an enlarged cross-sectional view of the multi-purpose tool, taken along the line 31-31 of FIG. 30 , showing the end guide tool in front elevation.

FIG. 32 is an enlarged and fragmentary cross-sectional view of the multi-purpose tool similar to FIG. 31 , shown attached to the end guide tool and also showing a sliding engagement stage of attachment to the driver (shown in front elevation).

FIG. 33 is an enlarged and fragmentary front elevational view similar to FIG. 32 , showing the driver nut fastener in the intermediate position shown in FIG. 27 .

FIG. 34 is an enlarged and fragmentary front elevational view similar to FIG. 33 , showing the driver in fixed engagement with the guide tool.

FIG. 35 is an enlarged and fragmentary view similar to FIG. 34 , showing the driver in fixed engagement with the guide tool and with the driver nut fastener shown in cross-section as in FIG. 28 , and the multi-purpose tool shown in cross-section as in FIG. 32 .

FIG. 36 is a partial and generally schematic cross-sectional view of a patient's spine, showing a thin guide pin installed at a first side thereof and a bone screw tap tool and threaded bore made thereby at a second side thereof.

FIG. 37 is a partial and generally schematic view of a patient's spine showing a tool assembly according to the invention with attached bone screw being guided toward the threaded bore in a vertebra in an early stage of a process according to the invention.

FIG. 38 is a partial and generally schematic view of a patient's spine, showing an end guide tool and the multi-purpose tool of the present invention being positioned for use in a process according to the invention.

FIG. 39 is a partial and generally schematic view of a patient's spine, showing a pair of end tools and a pair of intermediate tools of the present invention being positioned for use in a process according to the invention.

FIG. 40 is a partial and generally schematic view of a patient's spine, showing a pair of end tools with the flexible tangs containing a rod which has now been inserted and a pair of intermediate tools of the present invention with one of the intermediate tools shown with an attached multi-purpose tool in a rod reduction application and one of the end guide tools shown partially cut-away, illustrating a closure top installation tool disposed within the end tool and cooperating with a bone screw closure member, the tools being utilized in an early stage of rod implantation to guide the rod toward the bone screws.

FIG. 41 is a partial and generally schematic cross-sectional view of the spine, taken along the line 41-41 of FIG. 40 , showing an early stage of implanting a rod according to a process of the invention.

FIG. 42 is a partial and generally schematic view of a patient's spine similar to FIG. 40 , showing cut-away portions of all four tool assemblies, illustrating an intermediate stage of implanting a rod.

FIG. 43 is a partial and generally schematic view of a patient's spine similar to FIG. 42 , showing cut-away portions of three of the tool assemblies and one assembly without an end tool, illustrating the rod fully installed in all the bone screws.

FIG. 44 is an exploded front elevational view of an anti-torque tool assembly according to the present invention showing an antitorque tool and a closure top installation tool cooperating with a break-away bone screw closure member.

FIG. 45 is a bottom plan view of the anti-torque tool shown in FIG. 44 .

FIG. 46 is a fragmentary and front elevational view of a bone screw with attached break-away closure member and installed rod, and further showing the closure top installation tool of FIG. 44 with the anti-torque tool.

FIG. 47 is a fragmentary and front elevational view of a bone screw and anti-torque tool with portions broken away to show a torque driver advancing toward the break-away closure member in a process according to the invention.

FIG. 48 is a fragmentary and front elevational view of the bone screw and anti-torque tool similar to FIG. 47 , with portions broken away to show a fully installed rod and closure member with the break-away head removed from the top by the torque driver.

FIG. 49 is an enlarged and fragmentary front elevational view showing an alternative snap- or twist-on and twist-off attachment structure according to the invention on a guide tool and on a cooperating polyaxial bone screw head.

FIG. 50 is an enlarged and fragmentary front elevational view of the attachment structure shown in FIG. 49 showing the guide tool installed on the bone screw head.

FIG. 51 is an enlarged and fragmentary view of the attachment structure shown in FIG. 49 with portions removed to show the detail thereof showing an early stage of the snap on installation of the guide tool on the bone screw head.

FIG. 52 is an enlarged and fragmentary view similar to FIG. 51 showing a later stage of installation of the guide tool on the bone screw head.

FIG. 53 is an enlarged and fragmentary view similar to FIGS. 51 and 52 showing the guide tool installed on the bone screw head.

FIG. 54 is an enlarged and fragmentary front elevational view of a polyaxial bone screw shank with a pivotally attached head or receiver and shown with a guide tool, with portions broken away to show the detail thereof, illustrating a second alternative snap-on and pry-off attachment structure according to the invention on a guide tool and on the polyaxial bone screw head, showing and early stage of snap-on installation.

FIG. 55 is an enlarged and fragmentary view, identical to FIG. 54 with the exception that an intermediate stage of snap-on installation is shown.

FIG. 56 is an enlarged and fragmentary view, identical to FIG. 54 with the exception that the guide tool is shown fully installed on the bone screw head.

FIG. 57 is an exploded perspective view of a bone screw having a shank and a head or receiver, the receiver having a third alternative snap-on or slide-on and slide-off or push-off attachment structure according to the invention.

FIG. 58 is an enlarged front elevational view of the receiver of FIG. 57 .

FIG. 59 is an enlarged side elevational view of the receiver and shank of FIG. 57 shown with a guide tool with cooperating attachment structure.

DETAILED DESCRIPTION OF THE INVENTION

As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure.

With reference to FIG. 1 , and for example, also FIGS. 37 and 40 , reference numeral 1 generally designates a tool assembly according to the present invention and reference numeral 2 generally designates a tool set according to the invention, made up of a number and variety of tool assemblies 1 for use in installing a set of bone screws 4 into a patient's spine 6, followed by the installation of an orthopedic spinal rod or longitudinal member 8 into the bone screws 4 in a process according to the present invention.

The tool embodiment assembly 1 includes an end guide tool 9 or an intermediate guide tool 10 mated with a multi-purpose installation tool 12 configured to function as a guide tool stabilizer and supporter, a tang container and deployer and a rod pusher and reducer. The tool assembly 1 may further include a driver 14. A set 2 of the illustrated embodiment includes a pair of end guide tools 9 and a plurality of intermediate guide tools 10, which in the illustrated embodiment includes a pair of intermediate guide tools 10 on each side of a patient's spine 6, but which can include none, one or many intermediate guide tools 10 depending upon the particular application, so that one intermediate guide tool 10 is used for each intermediate bone screw 4 to which the rod 8 is to be attached.

The driver 14 is used in conjunction with the guide tool 9 and the guide tool 10 to implant bone screws 4 in the patient's spine 6 and, in particular, in vertebrae 16 along the spine 6 as shown in FIG. 37 . Each end guide tool 9 and intermediate guide tool 10 is configured to cooperate with the multi-purpose installation tool 12 to install the rod 8. However, it may be sufficient according to a process of the invention to not utilize the multi-purpose installation tool 12 or to use only one multi-purpose installation tool 12 in a particular tool set 2, as shown in FIG. 40 . Rods 8 or other longitudinal members are often installed on both sides of the spine 6 during the same procedure.

It is noted that any reference to the words top, bottom, up and down, and the like, in this application refers to the alignment shown in the various drawing figures, as well as the normal connotations applied to such devices, and is not intended to restrict positioning of the assembly 1 or the tool set 2 in actual use.

The end guide tool 9 is illustrated in FIG. 1 and FIGS. 5 through 8 . In particular, each end guide tool 9 has an elongate body 18 that is sized and shaped to be sufficiently long to extend from implanted bone screws 4 through an exterior of a patient's skin 20 so as to provide an outwardly extending and upper handle portion 22 that allows and provides for gripping by a surgeon during procedures utilizing the tool set 2, with or without an attached multi-purpose installation tool 12 and/or driver 14.

Each of the end guide tools 9 further includes an intermediate portion 24 and a lower implant engaging portion 26 which includes opposed implant engaging members for securing one the implants there between. Each end guide tool 9 has a substantially flat back wall 28 joining a pair of substantially cylindrically shaped side walls 32 and 33. The back wall 28 provides a flexible holding structure that includes a pair of parallel slits 34 extending from near the lower handle portion 22 to an end 36 of the tool 9. When pressed upon by a rod 8, a flap or flexible tang 38 disposed between the slits 34 in the back wall portion is configured to flex or spring radially outwardly from the bottom and about the top thereof in a deployed position, as is shown in FIG. 6 . The back wall portion flap or tang 38 provides a surgeon with some additional working space and flexibility when working with the rod 8 during surgery, so the rod 8 can extend beyond the bone screws 4 while remaining under resilient tension produced by outward biasing of the flexible back wall portion so that the rod 8 remains in a desired position and under control. Further, the tang or flap 38 also functions to urge the rod 8 toward the other tools in the tool set 2, as shown in FIG. 40 and as will be discussed more fully below.

The upper portion 22 of each end guide tool 9 includes a laterally or sideways opening channel 39, forming a U-shaped cross-section, a C-shaped cross-section, a crescent shaped cross-section or the like having a generally elongate and axially extending opening 40 with a side-to-side width 42. Preferably, the channel 39 mates with other channel structure described below so as to extend the entire length of the end guide tool 9. The opening 40 communicates with and forms part of the channel 39 that opens at an upper end 43 of the guide tool 9 and also opens perpendicularly with respect to a central axis of the guide tool 9 or laterally to one side of the end guide tool 9, thus defining the opening 40. The opening 40 narrows near the upper end 43 providing a slot 44 having a side-to-side width 45 that is smaller than the side-to-side width 42. The slot 44 is configured for sliding engagement with a rotational locking pin 46 disposed on the driver 14 and discussed more fully below. Disposed on either side of the slot 44 are co-planar surfaces 47 and 48 that are parallel with the back wall 28. The surfaces 47 and 48, as well as the back wall 28, provide alignment surfaces when the multi-purpose tool 12 is inserted onto the guide tool 9 discussed more fully below.

The opening 40 is of substantially constant width through a mid-section 48 of the handle portion 22, sufficiently wide to receive additional tools and/or a closure top for sideways loading into the channel 39, as will be discussed below.

The upper portion 22 also includes an outer helically wound discontinuous guide and advancement structure 50 disposed on outer surfaces of both of the substantially cylindrically shaped side walls 32 and 33, which may include conventional helically wound V type threads, buttress threads, helically wound square threads, or other guide and advancement structure to cooperate with equivalent or mateable structure within the multi-purpose installation tool 12 and the driver 14, as described more fully below. The advancement structure 50 extends from near the intermediate portion 24 to the open end 43. The back wall 28 extending between the threaded sides 32 and 33 has an outer substantially planar and smooth surface finish.

Extending from the upper portion 22 and into the intermediate portion 24 of each end guide tool 9 is an outward facing channel 51 that has an opening 52 with a side-to-side width 53 that is somewhat smaller than the width 42 of the upper handle portion 22, such that the channel 51 and opening 52 are sized and shaped to receive and allow passage of certain tools and implants, as described below.

Furthermore, a remaining portion of the end guide tool intermediate portion 24 and the lower portion 26 includes a groove or channel 55, with an elongate, axially extending and radially outward opening 57, having a side-to-side width 58 that is slightly smaller than the width 42 of the opening 40, but larger than the slot width 45 and the opening width 53. The channel opening 57 is disposed opposite the flexible tang or flap 38. All of the channels 39, 51 and 55 communicate with one another and are aligned with one another so as to provide a continuous elongate interior and sideways open passageway with an open side from near the top end 43 to near the bottom 36 thereof. This passageway provides a continuous open path of non-uniform cross-sectional radius throughout from the top 43 to the bottom 36 thereof that is parallel to an elongate axis A of each end guide tool 9. As will be discussed more fully below, each end guide tool channel opening 57 is sized and shaped to slidingly receive a respective end 59 of the rod 8 therein. It is foreseen that one or all of the channel openings forming the open side that extends from near the top end 43 to near the bottom 36 of the guide tool 9 may be sized and shaped to receive the end 59 of the rod 8. It is also foreseen that the rod 8 may be of uniform or non-uniform diameter, regular or uneven surface construction, or smooth or roughened surface finish, and that the channel openings may in turn be sized and shaped to receive such a rod end that may exhibit a greater or smaller width or diameter than at other locations along the rod.

The slits 34 are spaced in order to have a back wall or flap flex region having a size and shape to allow at least partial passage of a respective end 59 of the rod 8 between the side walls 32 and 33. Also located near the end guide bottom 36 is a rod abutment recess 61 that is sized and shaped for the purpose of bridging the rod 8 when the end guide tool 9 is rotated for removal, as described below. However, it is foreseen that other removal means could be used. The end guide tool 9 also receives a closure top 62, as will be described below. Still further, near the bottom 36 of each of the end guides 9 on inner surfaces of the side walls 32 and 33, is a helical wound, discontinuous guide and advancement structure 64 which may include conventional helically wound V-shaped threads, buttress threads, reverse angle threads, helically wound square threads, or other guide and advancement structure to cooperate with equivalent or mateable structure within the bone screw heads 4 and on the closure top 62, as also described below.

At the lower portion 26, the substantially cylindrical side walls 32 and 33 include an outer radially extending bevel 66 and substantially cylindrical outer side walls 68 and 69, respectively. The walls 68 and 69 uniformly increase the thickness of the respective side walls 32 and 33, resulting in a substantially cylindrical cross-section of greater diameter than a diameter created by an outer surface of the side walls 32 and 33 at the intermediate portion 24.

As will be discussed more fully below, in addition to increasing the diameter, the walls 68 and 69 are configured with co-planar front walls or facets 70 and co-planar back walls or facets 71 with the facets 70 being disposed parallel to the facets 71, providing for alignment and mating with an interior of the multi-purpose installation tool 12 to ensure that the end guide tool 9 is retained in a selected, non-rotatable position with respect to the multi-purpose installation tool 12 when installed therein. Each of the walls 68 and 69 can include an abutment pin 67 located at an outer surface thereof and near the bottom or end 36. The pin 67 may serve as a stop for the multi-purpose installation tool 12 as will be described more fully below; however, such a pin stop is not always needed.

Near the end or bottom 36 of each end guide tool 9, disposed on an inner surface of each of the side walls 32 and 33, is a radially inward facing attachment structure, generally 72, that will be described below in conjunction with a similar structure on the intermediate guide tool 10 and the bone screw 4.

Each of the intermediate guide tools 10, specifically illustrated in FIGS. 2 to 4 , have a somewhat similar overall shape when compared to the end guide tools 9 in that both are preferably of the same axial length and width and also have much structure in common; however with certain differences as noted. Each intermediate guide tool 10 has an overall elongate body 74 with an upper handle portion 76, an intermediate portion 77 and a lower implant engaging portion 78 which includes opposed implant engaging members for securing one of the implants there between. In the upper portion 76, the body 74 is generally C-shaped defining a radially outward opening 79 communicating with an elongate and axially extending channel 80 defined by a rear wall 81 having a lower web edge 96 and side walls 82 and 83. With reference to FIG. 2 , the channel 80 front opening 79 extends parallel to an axis B of the body 74 and has a side-to-side width 85 configured to receive tools and elements described below.

Similar to the end guide tool 9, the opening 85 narrows near an upper end 87 providing an elongate slot 88 having a side-to-side width 89 that is smaller than the width 85. The slot 88 is configured for sliding engagement with the pin 46 disposed on the driver 14 and discussed more fully below. Disposed on either side of the slot 88 are co-planar surfaces 91 and 92 that are parallel with the rear wall 81. The surfaces 91 and 92, as well as the rear wall 81, provide alignment surfaces when the multi-purpose tool 12 is inserted onto the guide tool 10, discussed more fully below. Below the slot 88, the side-to-side opening width 85 is substantially constant through a mid-section 90 of the handle portion 76, sufficient to receive additional tools and/or a closure top, as will be discussed below.

The upper or handle portion 76 also includes an outer helically wound discontinuous guide and advancement structure 93 disposed on outer sides of both of the substantially cylindrically shaped side walls 82 and 83, which may include conventional helically wound V-threads, helically wound square threads, buttress threads or other guide and advancement structure to cooperate with equivalent or mateable structure within the multi-purpose installation tool 12 and the driver 14 as described more fully below. The advancement structure 93 extends from near the intermediate portion 77 to the open end 87. An outer surface of the rear wall 81 extending between the threaded sides 32 and 33 is substantially planar and smooth.

The upper or handle portion 76 further includes an outward facing channel 94 communicating with the channel 80. The channel 94 is defined in part by a rear wall or web 95 having a lower end with the web edge 96, the wall 95 being integral with the wall 81. Communicating with the channel 94 is an elongate and axially extending opening 98 having a side-to-side width 99 that is somewhat smaller than the width 85 of the opening 79. The opening 98 is further defined by the walls 82 and 83. The channel 94 and opening 98 are configured to receive, contain and allow translational movement therealong or rotational relative movement of certain tools, as described more fully below. Although not shown in the drawings, it is foreseen that the channel 94, channel opening 98 and rear wall or web 95 may extend into the intermediate portion 77 to provide greater strength and stability to the lower portion 78 of the intermediate tool 10, with the opening 98 also extending into the lower portion 78 providing greater retention of small tools or parts being inserted through the channel 94.

The intermediate portion 77 of the intermediate tool 10 includes two spaced side walls or legs 102 and 103, extending from and integral with the side walls 82 and 83, respectively. The legs 102 and 103 have outer surfaces that are partially cylindrical.

Similar to the end tool 9, at the juncture of the intermediate portion 77 and the lower portion 78, each of the legs 102 and 103 include an outwardly facing radially extending bevel 106 integral with substantially cylindrical outer side walls 107 and 108, respectively. The outer walls 107 and 108 extend along the length of the lower portion 78 and uniformly increase the thickness of the respective legs 102 and 103, resulting in a substantially cylindrical cross-section of greater outer diameter at the lower portion 78 than an outer diameter created by the outer surfaces of the legs 102 and 103 along the intermediate portion 77. As will be discussed more fully below, in addition to increasing the diameter, the walls 107 and 108 are configured with co-planar front facets or walls with flat surfaces 109 and co-planar rear facets or walls with flat surfaces 110, the facets 109 disposed parallel to the facets 110, providing for alignment with an interior of the multi-purpose installation tool 12 to ensure that the intermediate guide tool 10 is properly mated with and retained in a selected, non-rotatable position with respect to the multi-purpose installation tool 12 when installed therein.

Along both the intermediate and lower portions 77 and 78 of the intermediate tool 10, the legs 102 and 103 define an elongate and axially extending passthrough slot 111 sized and shaped to slidingly receive the rod 8. The slot or opening extends from the lower edge of the web end 96 of the rear wall 95 to an open end or bottom 112 of the tool 10 configured to secure an open ended spinal surgery implant there between.

Near the bottom 112 of each implant engaging leg member 102 and 103 of the intermediate guide tool 10 is a helically wound but discontinuous square thread 114 and it is foreseen that other type of guide and advancement structure may be utilized such as helically wound flange forms, reverse angle threads, buttress threads, etc. The thread form 114 cooperates with the closure top 62, as described below. The lower end of each leg 102 and 103 of the intermediate guide tool 10 also includes a cutout or rod-abutment recess 116 similar to the recess 61 described with respect to the end tool 9. Each of the walls 107 and 108 can include an abutment pin 118 located at an outer surface thereof and near the bottom or end 112. The pin 118 may serve as a stop for the multi-purpose installation tool 12 as will be described more fully below.

Also near the end or bottom 112 of each leg 102 and 103 of the intermediate guide tool 10, disposed on inner substantially cylindrical surfaces 120 and 121, respectively, is a radially inward facing attachment structure, generally 124, substantially similar to the structure 72 disposed on the end guide tool 9. The structure 124 will be described herein in conjunction with the bone screw 4.

With reference to FIGS. 9-11 , the embodiment shown includes an attachment structure 124 having a first projection, stop or pin 126 in spaced relation with a second smaller projection, stop or pin 127, both pins being disposed on the surface 120. In the embodiment shown, the structure 123 further includes a cooperating third projection, stop or pin 130 in spaced relation with a fourth smaller projection, stop or pin 131, the pins 130 and 131 being disposed on the surface 121.

The larger pins 126 and 130 are substantially configured the same, both being substantially rounded, radially inward projecting nodules, each having a ridge or lip 132 and 133, respectively, projecting upwardly toward the guide and advancement structure 114 and that preferably follows the curvature of the respective leg inner surface 120 and 121.

The lips 132 and 133 with respective surfaces 120 and 121 define slots 134 and 135, respectively, for receiving the bone screw 4 as will be discussed more fully below. The pin 126 is configured slightly larger than the pin 130, requiring similar modification in the bone screw 4, resulting in a method of operation wherein the bone screw 4 may only be mated with the guide 9 or 10 from a single direction, ensuring appropriate alignment between the bone screw 4 and guide tool advancement structure 114 with respect to the installment of the closure top 62.

Each of the larger pins 126 and 130 is also disposed at substantially the same distance from respective bottom surfaces 138 and 139, at the end 112 of the guide tool 10 and adjacent a rod-abutment recess 116. Furthermore, each of the larger pins 126 and 130 is also disposed at substantially the same distance from respective parallel seating surfaces 140 and 141, that form a base of the guide and advancement structure 114. Additionally, in this embodiment the pins 126 and 130 are disposed in diametrically opposed relation when viewed in cross-section as shown in FIG. 10 .

The smaller pins 127 and 131 are also substantially configured the same, the pin 131 being slightly larger than the pin 127, but otherwise both pins 127 and 131 being substantially rounded, radially inwardly projecting nubs, each disposed at substantially the same distance from the respective bottom surfaces 138 and 139 and the respective seating surfaces 140 and 141. Furthermore, the pins 127 and 131 are disposed in diametrically opposed relation when viewed in cross-section as shown in FIG. 10 . Each of the pins 127 and 131 are disposed closer to the respective end surfaces 138 and 139 than are the larger pins 126 and 130. It is noted that other orientations and pin sizes may be utilized according to the invention, with the pin sizes and locations cooperating with respective features on the bone screws 4. Preferably, the pins are of different sizes to provide for mating of the guide tool 9 or 10 with the bone screw 4 from a single direction, resulting in a desired alignment between the bone screw 4 guide and advancement structure 114 and the closure top 62 guide and advancement structure.

The pins 126, 127, 130 and 131 cooperate and mate with the bone screw 4, at a receiver portion, generally identified by the reference numeral 145, of a head 146 thereof. With reference to FIGS. 12-15 , each of the bone screws 4 further includes a threaded shank 148 attached to the head 146, the shank 148 for screwing into and seating in a vertebra 16 that is part of the human spine 6. The head 146 includes first and second arms 150 and 151 that define a rod receiving channel 153 passing therethrough. Each of the bone screw shanks 148 includes an upper portion 154 that extends into the head 146 and is operationally secured therein, so that the head 146 is rotatable on the shank 148 until locked in position through engagement with the rod 8 under pressure.

The receiver portion 145 is disposed on outer surfaces of the arms 150 and 151. The receiver portion 145 of arm 150 includes a slot or groove 158 communicating with a recess 159 defined in part by a flange 160. The groove 158 and recess 159 open at a front surface 162 of the arm 150 and extend across a facet 163 and into a side surface 164 thereof. With reference to FIG. 21 , the groove 158 is configured to mate with the large pin 126 with the lip 132 extending into the recess 159 and the flange 160 disposed in the slot 134 when the guide tool 10 is attached to the bone screw head 146. The width of the slot 134 is sized to prevent passage therethrough of the pin 126 except by twisting or rotational relative movement therebetween. The receiver portion 145 of the arm 150 further includes a rounded aperture 165 disposed substantially centrally on a face or facet 167 of the arm 150, the facet 167 disposed adjacent to the side surface 163. The aperture 165 is configured to mate with the small pin 127.

Similar to the arm 150, the receiver portion 145 of the arm 151 defines a groove 168 communicating with a recess 169 defined in part by a flange 170. The groove 168 and recess 169 open at a back surface 172 of the arm 151 and extend across a facet 173 into a side surface 174 thereof.

Similar to what is shown in FIG. 21 with respect to the arm 150, the groove 168 is configured to mate with the large pin 130 with the lip 133 extending into the recess 169 and the flange 170 disposed in the slot 135 when the guide tool 10 is attached to the bone screw head 146. The receiver portion 145 of the arm 151 further includes a rounded aperture 175 disposed substantially centrally on a face or facet 177 of the arm 151, the facet 177 disposed adjacent to the side surface 173. The aperture 175 is configured to mate with the small pin 131.

In the embodiment shown, to attach the bone screw head 146 to the guide tool 10, the guide tool 10 is rotated about its axis B such that the legs 102 and 103 are lowered into place as shown in FIGS. 17 and 18 , with the facets 167 and 177 of the head 146 disposed between the guide tool legs 102 and 103, with the facet 167 adjacent the leg 102 and the facet 177 adjacent the leg 103, thereby aligning the groove 158 with the large pin 126 and the groove 168 with the large pin 130. The head 146 may then be twisted into place as shown by the arrow T in FIGS. 18, 19 and 20 . The legs 102 and 103 may splay slightly as the head is twisted into place, but come to rest in a generally non-splayed configuration and held in place by the structure of the attachment mechanism to resist splaying.

In order to disengage the guide tool 9 or the guide tool 10 from the bone screw 4, the guide tool 9, 10 is rotated counterclockwise from an attaching configuration (opposite to the arrow T), when viewing from the top so as to disengage the lips 132 and 133 from the recesses 159 and 169, respectively. In this manner, end guide tools 9 and intermediate guide tools 10 that have previously twisted on, now twist off of respective bone screws 4.

While a preferred embodiment of the invention has the respective pins of the attachment structure on the guide tools and the grooves on the bone screw heads, it is foreseen that these elements could be reversed in total or part in accordance with the invention. Also, other suitable attachment structure could be used, such as sloped or tapered undercut surfaces on the screw heads that overlap, mate and interlock with radially or linearly projecting structure on or near the ends of the guide tools. Such projecting structure can be snapped on or clipped on and translated up to provide for anti-splay overlapping surfaces. In addition, a groove could be put in the outer surface of the screw head and a fin on the guide tool could snap or slide into the groove.

In the embodiment shown, the recesses 61 and 116 disposed on the respective guide tools 9 and 10 are sized, shaped and positioned so that when the rod 8 is located in the bone screws 4, the guide tools 9 and 10 can rotate about respective axes A and B, with the recess 61 and 116 allowing the respective guide tool 9 and 10 to straddle over the rod 8, thereby allowing the guide tool 9 and 10 to twist relative to the bone screw 4 and free the attachment structures 72 and 124 from the receiver portion 145 of the bone screw 4 and thereafter be removed after all procedures are complete, as described below.

The closure top 62 closes between the spaced bone screw arms 150 and 151 to secure the rod 8 in the channel 153. The closure top 62 can be any of many different plug type closures. With reference to FIGS. 46-48 , preferably the closure top 62 has a cylindrical body 180 that has a helically wound mating guide and advancement structure 181. The guide and advancement structure 181 can be of any type, including V-type threads, buttress threads, reverse angle threads, or square threads. Preferably the guide and advancement structure 181 is a helically wound flange form that interlocks with a reciprocal flange form as part of a guide and advancement structure 183 on the interior of the bone screw arms 150 and 151.

A suitable locking guide and advancement structure of this type is disclosed in U.S. Pat. No. 6,726,689 from Ser. No. 10/236,123 which is incorporated herein by reference. The helically wound guide and advancement structures 64 and 114 in the respective guide tools 9 and 10 are sized and shaped to receive the mating guide and advancement structure 181 of the closure top 62 and align with the guide and advancement structure 183 of the bone screw 4 to form a generally continuous helically wound pathway, but does not require locking between the closure top 62 and the tools 9 and 10, even when an interlocking flange form is utilized on the closure top 62.

The guides 64 and 114 allow the closure top 62 to be rotated and the surgeon to develop mechanical advantage to urge or drive the rod 8, while still outside or partially outside the bone screw 4, toward and into the bone screw head 146. This is especially helpful where the rod 8 is bent relative to the location of the vertebra 16 (which is sometimes the case) to which the rod 8 is to attach and is not easily placed in the bone screw head 146 without force and the mechanical advantage provided by the guides 64 and 114. In particular, the guide and advancement structures 64 and 114 on the respective tools 9 and 10 are located and positioned to align with the guide and advancement structure 183 on the insides of the bone screw arms 150 and 151, as shown in FIG. 42 and pass the closure top 62 therebetween while allowing the closure top 62 to continue to rotate and to continuously apply force to the rod 8, so as to aid in seating the rod 8 in the bone screw head 146.

Each closure top 62 also preferably includes a break-off head 186 that breaks from the cylindrical body 180 in a break-off region 187 upon the application of a preselected torque, such as 95 to 120 inch-pounds. The break-off head 186 preferably has a hexagonal cross section faceted exterior that is configured to mate with a similarly shaped socket of a final closure driving or torquing tool 190 described below. It is foreseen that different driving heads or other methods of driving the closure top 62 can be utilized with certain embodiments of the invention, such as non-break-off closure top designs.

The present invention is not intended to be restricted to a particular type of bone screw, bone screw closure mechanism, or bone screw and guide tool attachment mechanism. In the present embodiment, a polyaxial type bone screw 4 is utilized wherein the shank 148 is locked in position by direct contact with the rod 8. It is foreseen that the tool set 2 of the present invention can be used with virtually any type of bone screw, including fixed monoaxial and polyaxial bone screws of many different types wherein the head is locked relative to the shank by structure other than in the manner described in the illustrated embodiment. It is also foreseen that the screws could be cannulated.

With reference to FIGS. 22-25 , the multi-purpose installation tool 12 of the tool assembly 1 of the invention includes an upper translation nut 202 rotatably and free wheelingably attached to a lower guide tool stabilizer or support sleeve 204. The sleeve 204 has an inner substantially cylindrical surface 205 defining a substantially hollow passageway 206 sized and shaped to slidingly receive an end tool 9 or an intermediate tool 10 therein. Alternatively, is foreseen that the sleeve could have an inner and outer planar surface. The sleeve 204 is elongate and includes a receiving end 207, a substantially cylindrical outer body 208 and a translation nut attachment end portion 210 disposed opposite the receiving end 207. The receiving end 207 not only functions to receive the guide tool 9 or 10 into the sleeve 204, but also as a pressing block 218 for contacting the flexible flap or spring tang 38 and as a pressing end 207 for contacting the rod 8 and translating the rod 8 toward the bone screw head 146 when the multi-purpose installation tool 12 is installed on the guide tool 9 or 10, as will be discussed more fully below.

The cylindrical body 208 further defines a slotted U-shaped or C-shaped channel 212 that opens radially at an opening 213 and also opens at the receiving end 207 and extends substantially along a length of the body 208 to a location 214 spaced from the nut attachment end portion 210. The channel opening has a side-to-side width 216 sized to receive the back wall tang portion or flexible flap 38 of the end guide tool 9 therethrough, when aligned therewith. For example, with reference to FIG. 38 , the multi-purpose installation tool 12 is shown partially removed from an end guide tool 9 and deploying the tang 38 after the bone screw has been inserted. Because of the substantial length of the channel 212 as defined by the location 214 and because of the channel width 216, the multi-purpose installation tool 12 can be removed, turned 180 degree. and reattached to the end guide tool 9 thereby providing access through the channel opening 213 for protrusion of the back wall tang portion or flap 38 of the end guide tool 9. The flap 38 is thus not encumbered or restricted by the tool 12 during the rod pushing application and the flap 38 can be flexed outwardly by a rod 8 (not shown) or other forces, when the devices are assembled in this configuration.

Disposed flush to the lower sleeve end 207 and rigidly attached to the inner cylindrical surface 205 is the solid guide tool alignment and tang/rod pressing block 218. The block 218 has a substantially smooth, planar and rectangular surface 220 facing inwardly radially from the inner surface 205. The block 218 also follows the curve of the cylindrical surface 220 at a surface 222 thereof. Thus, as shown in FIG. 24 , the block 218 has a segment shape when observed from a bottom plan view. The term segment used herein is defined as the part of a circular area bounded by a chord and an arc of a circle cut off by the chord. This segment shape of the block 218 provides a mechanical advantage for compressing the flexible flap 38 flush with the end guide tool 9 and for advancing the rod 8 into the bone screw 4 with the multi-purpose installation tool 12 which will be discussed more fully below.

The flat, rectangular surface 220 provides structure for installing the guide tool 9 or 10 in a mating and desired alignment with respect to the multi-purpose installation tool 12. For example, with respect to the guide tool 10, a preferred alignment is that the rear wall 81 of the tool 10 be disposed adjacent to the surface 220 when inserting the tool 10 into the multi-purpose installation tool 12. Then, the tool 10 is slid into the multi-purpose tool sleeve 204, with the block 218 preventing axial rotation of the tool 10 with respect to the sleeve 204, and resulting in the preferred alignment of the opening 79 and the pass-through slot 11 of the tool 10 and the U-shaped channel 212 of the multi-purpose tool in this application.

With respect to the end guide tool 9, the block 218 with the planar surface 220 provides for the insertion of the tool 9 in a first, installation tang containing position or a second, rod pushing position. When utilizing the assembly 1 of the invention to install a bone screw 4, it is advantageous for the flexible back wall portion or tang 38 of the tool 9 to be fully restrained by the multi-purpose installation tool 12 and for the walls 68 and 69 to be locked in a non-splayable or anti-splay position. Therefore, in the first, bone screw installation tang containing position, the multi-purpose installation tool 12 is inserted onto the tool 9 with the back wall 28 of the tool 9 disposed adjacent to the sleeve surface 220. Then, the tool 9 and the sleeve 204 are attached with the block 218 preventing axial rotation of the tool 9 with respect to the multi-purpose installation tool 12. This results in the preferred alignment wherein the flexible back wall portion or tang 38 is disposed adjacent to the multi-purpose tool sleeve 204 and contained and disposed opposite the U-shaped channel 212. After the bone screw 4 is installed and it is desired to install the rod 8 in two or more bone screws 4, the multi-purpose installation tool 12 is removed from the end guide tool 9 and replaced thereon with the slot 44 and channel openings 40 and 94 adjacent to and facing the alignment block 218.

The translation nut 202 of the multi-purpose installation tool 12 is substantially cylindrical in shape and is shown with outer grooves 223 to aid a surgeon in handling the multi-purpose installation tool 12 and rotating the nut 202. The nut 202 further includes an inner cylindrical surface 224 defining an inner substantially cylindrical passage 226 communicating with the passage 206 of the sleeve 204. The inner surface 224 further includes a helical guide and advancement structure as shown by a V-shaped thread 228 that is configured to mate with the guide and advancement structure 50 of the end guide tool 9 or the guide and advancement structure 93 of the intermediate guide tool 10.

With reference to FIG. 25 , the inner cylindrical surface 224 extends from an upper open end 230 of the translation nut 202 to an annular seating surface 232 extending radially outwardly and perpendicular to the cylindrical surface 224. As will be discussed more fully below, the surface 224 with associated thread 228 is of a length that provides an equivalent translation distance of the multi-purpose installation tool 12, and in particular the tang/rod pressing block 218, with respect to the guide tool 9 or 10 such that the pressing block 218 can be used to gradually push the rod 8 toward the bone screw 4 for the entire translation distance by rotating the nut 202 which can be continued until the rod is fully seated in the head of the bone screw.

Also with reference to FIG. 25 , at the annular seating surface 232, the sleeve 204 is in sliding contact with the nut 202. A lower portion 234 of the nut 202 further defines a second inner cylindrical surface 236 of greater diameter than the surface 224. The surface 236 has a diameter slightly greater than a diameter of the sleeve 204 and is configured to slidingly receive the sleeve 204 into the nut 202 along the surface 236. The nut 202 further defines an annular recess or groove 238 configured to receive a pin 240 rigidly fixed to the sleeve 204. The pin 240 may be accessed for attachment and removal from the sleeve 204 through an aperture 242 disposed in the translation nut 202. The pin 240 slidingly mates with the nut 202 within the recess 238, keeping the nut 202 and sleeve 204 in an attached but freely rotatable relation.

With reference to FIGS. 26-28 , the driver 14 of an assembly 1 according to the invention includes a handle 250, a guide tool fastener or nut 252, and an elongate cylindrical stem or shaft 254 having a lower cylindrical portion 255 integral with a bone screw engager shown as a socket 256. The socket 256 is configured to mate with the upper part of the bone screw shank 154. The shaft 254 with attached socket 256 is receivable in and passes through the interior of the guides 9 and 10, such as the channel 80 of the guide tool 10. The lower portion 255 has a slightly smaller diameter than a diameter of the remainder of the shaft 254, this smaller diameter provides for adequate clearance of the portion 254 from the guide and advancement structures 64 and 114 when the shaft 254 is installed within the interior of the respective guide tools 9 and 10. The stem or shaft 254 is rigidly attached to the handle 250 and coaxial therewith. Both the handle 250 and the guide tool fastener 252 include outer grooves 258 and 259 respectively, about outer cylindrical surfaces thereof to aid in gripping and rotating the respective components.

The guide tool fastener 252 is a substantially hollow cylinder disposed in coaxial relationship with the handle 250 and the shaft 254. The fastener has a threaded inner cylindrical surface 262 disposed at a lower portion 263 thereof, the threaded surface 262 configured to mate with the guide and advancement structure 50 of the end guide tool 9 or the guide and advancement structure 93 of the intermediate guide tool 10. The fastener 252 is disposed on the driver 14 between an annular surface 264 of the handle 250 and the pin 46 that is fixed to the shaft 254 and extends laterally therefrom.

The driver 12 further includes a lateral pin 266 projecting radially outwardly from a cylindrical surface 268 adjacent the handle 250. In the embodiment shown, the cylindrical surface 268 is integral with the handle 250 and fixedly attached to the shaft 254. The pin 266 is disposed within an annular recess 270 defined by the cylindrical surface 268, and surfaces of the fastener 252, including an upper seating surface 272, a lower seating surface 274 and an inner cylindrical surface 276. The pin 266 disposed in the recess 270 allows for both rotational and axial or vertical translational movements of the fastener 252 with respect to the shaft 254. Thus, as shown in FIG. 26 , the fastener 252 is rotatable about an axis C. Furthermore, the fastener is slidable along the axis C between the annular surface 264 and the pin 46, with FIG. 26 showing a first or unattached position with the fastener 252 in contact with the annular surface 264 and FIGS. 27 and 28 showing a second, engagement position, with the fastener 252 partially covering, but not contacting the pin 46, with the pin 266 abutting the upper seating surface 272 prohibiting further downward or vertical (axial) translational movement of the fastener 252 with respect to the shaft 254.

As stated previously herein, the pin 46 is configured for sliding engagement with both the slot 44 of the guide tool 9 and the slot 88 of the guide tool 10 when the driver shaft 254 is disposed in an interior of the guide tool 9 or 10. When the pin 46 is received in the slot 44 or the slot 88, any relative rotational movement between the guide tool 9 or 10 and the driver 14 is prevented, but the driver is free to slide axially with respect to the guide tool 9 or 10. When the fastener or nut 252 is slid into the second position shown in FIGS. 27 and 28 and the fastener is mated with the guide and advancement structure 50 of the end guide tool 9 or the guide and advancement structure 93 of the intermediate guide tool 10 by rotating the fastener 252 to a location adjacent to the pin 46, with the pin 266 in contact with the upper seating surface 272, relative axial movement between the driver 14 and the guide tool 9 or 10 is also prevented.

With reference to FIGS. 1 and 29-35 , a three-component assembly 1 according to the invention including the guide tool 9, the multi-purpose installation tool 12 and the driver 14 may be assembled as follows: The guide tool 9 shown with attached bone screw 4 is inserted into the multi-purpose installation tool 12 with the upper end 43 being inserted into the receiving end 207 of the multi-purpose installation tool 12. With respect to the assembly shown in FIGS. 29-31 , illustrated is a particular assembly wherein the multi-purpose installation tool 12 is being utilized as a support or stabilizer for the end guide tool 9 during installation of the bone screw 4 into the vertebra 16, specifically, to contain and compress the tang 38 and to provide extra support to the walls, such as walls 68 and 69 of tool 9. Thus, the guide tool 9 is received into the multi-purpose installation tool 12 with the rear wall 28 facing the alignment block 218 as shown in FIG. 29 .

As the guide tool 9 is received into the multi-purpose installation tool 12, rotational movement is prevented by the alignment block 218 in sliding contact with the flat surfaces 28 of the guide tool 9. The translation nut 202 is then rotated clock-wise as viewed from the top end 230 and shown by the arrow X, with the thread 50 of the guide tool 9 mating with the thread 228 disposed on the inner surface 224 of the translation nut 202. The translation nut 202 is preferably rotated until the upper end 43 of the guide tool 9 is positioned outside of the body of the nut 202 with a few of the threads 50 exposed as shown in FIGS. 30 and 31 . Furthermore, the sleeve 204 cannot be translated beyond the pin 67 that stops the sleeve near the rod abutment recess 61 disposed near the end of the guide tool 9. During rotation of the translation nut 202, the guide tool 9 is held in a preferred bone screw installation position and any rotational movement of the tool 9 is prevented by the alignment block 218 in contact with the co-planar back walls or facets 71 of the guide tool 9 as well as the planar back surface of the tang 38. As illustrated in FIGS. 30 and 31 , when the guide tool 9 is fully installed in the multi-purpose installation tool 12 in this first or bone screw installation position, the flexible back wall portion or flap 38 is compressed and retained in place between the side walls 32 and 33 by the alignment block 218.

When the multi-purpose installation tool 12 is used as a rod pusher with the guide tool 9 as shown in FIGS. 38 and 41 , the multi-purpose installation tool 12 is preferably used first as an end guide tool stabilizer and tang 38 container, as already described herein, and thus must first be removed by rotating the translation nut 202 counter-clockwise until the multi-purpose installation tool 12 is disengaged from the end tool guide 9 thereby deploying the tang 38. Thereafter, the multi-purpose installation tool 12 is removed and replaced on the guide tool 9 with the slot 44 and channel openings 40 and 94 adjacent to and facing the alignment block 218. As the multi-purpose installation tool 12 reinserted onto the guide tool 9, rotational movement is prevented by the alignment block 218 in sliding contact with the flat surfaces 47 and 48 of the guide tool 9. The translation nut 202 is then rotated clock-wise as shown by the arrow X (FIG. 29), with the thread 50 of the guide tool 9 mating with the thread 228 disposed on the inner surface 224 of the translation nut 202. Similar to what is shown in FIGS. 30 and 31 , the translation nut 202 is rotated clockwise as shown by the arrow X, until the upper end 43 of the guide tool 9 is positioned outside of the body of the nut 202 with some of the threads 50 exposed. During rotation of the translation nut 202, the guide tool 9 is held in position and any rotational movement of the tool 9 is prevented by the alignment block 218 in contact with the co-planar front walls or facets 70 of the guide tool 9. When the multi-purpose installation tool 12 is used in this second or rod pushing position, the flexible back wall tang portion or flap 38 is not obstructed by the sleeve 204 of the multi-purpose installation tool 12 and may spring out or be further pushed out through the opening 213 of the U-shaped channel 212.

An assembly 1 according to the invention may also include the intermediate guide tool 10 in the place of the guide tool 9 as shown in FIGS. 40-42 . Because the intermediate guide tool 10 includes a pass-through slot 111 rather than a flexible back wall tang portion 38, the alignment between the multi-purpose installation tool 12 and the guide tool 10 may be the same during bone screw installation as for the pushing of the rod 8. Therefore, the tool guide 10 may be inserted into the multi-purpose installation tool 12 with either the rear wall 81 or the slot 88 adjacent to and facing the alignment block 218.

Similar to the discussion herein with respect to the guide tool 9, as the guide tool 10 is inserted into the multi-purpose installation tool 12, rotational movement is prohibited by the alignment block 218 in sliding contact with either the rear wall 81 or the coplanar surfaces 91 and 92 of the guide tool 10. The translation nut 202 is then rotated clock-wise as viewed looking toward the top 87 of the tool 10, with the thread 93 of the guide tool 10 mating with the thread 228 disposed on the inner surface 224 of the translation nut. Similar to what is shown in FIGS. 30 and 31 , the translation nut 202 is rotated until the upper end 87 of the guide tool 10 is positioned outside of the body of the nut 202 with some of the threads 93 exposed. During rotation of the translation nut 202, the guide tool 10 is held in position, with rotational movement of the tool 10 being prevented by the alignment block 218 in contact with the co-planar front walls or facets 109 or the co-planar rear walls or facets 110 of the guide tool 10.

Further discussion of the assembly 1 in this application will be directed toward the end guide tool 9 shown in the drawings. Unless specifically stated otherwise, the intermediate guide tool 10 can be utilized in similar fashion to what is being described herein with respect to the end guide tool 9.

With reference to FIGS. 1 and 32-35 , after installation of the multi-purpose installation tool 12 to the guide tool 9, the driver 14 is inserted into the guide tool 9/multi-purpose installation tool 12 combination by inserting the socket end 256 into the end 43 of the guide tool 9 and sliding the shaft 254 into the interior of the guide tool 9 until the socket end 256 contacts and surrounds the upper part of the shank 154 of the bone screw 4 as shown in FIG. 35 . As the shaft 254 is being inserted into the guide tool 9, the pin 46 on the shaft 254 of the driver 14 is aligned with and slid into the slot 44 of the guide tool 9. In order to more easily view the pin alignment process, the guide tool fastener 252 is placed in the first or unattached position with the fastener 252 in contact with the annular surface 264 as shown in FIG. 32 . Also as shown in FIG. 32 , preferably, the pin 46 is slid to a position disposed substantially within the slot 44 when the socket end 256 engages the shank 154 of the bone screw 4. The guide tool fastener or nut 252 is then rotated clockwise as viewed from the handle and illustrated by the arrow Y in FIG. 33 , from the first unattached position toward the second engaged position, mating the thread 50 located near the end 43 of the guide tool 9 with the inner threaded surface 262 of the nut 252 of the driver 14. If, after the fastener 252 is rotated to a hand-tightened position, and a gap or space remains between the fastener 252 and the translation nut 202, as shown in FIG. 33 , the translation nut 202 may then be rotated counter-clockwise as shown by an arrow Z in FIG. 33 , and hand-tightened until the translation nut 202 abuts against the fastener 252, as shown in FIG. 34 . The assembly 1 is then fully assembled and may be used to install the bone screw 4 into the vertebra 16 as will be described more fully below. Thereafter, the driver 14 may be removed by rotating the fastener 252 in a counter-clockwise direction (arrow Z) and sliding the shaft 254 out of the multi-purpose installation tool 12 through the open end 230.

Another tool used in implanting a spinal rod 8 is an antitorque tool 300 illustrated in FIGS. 44 and 45 and further shown in FIG. 44 with a closure top installation tool 302 engaging the break-away portion 186 of the closure top 62. The closure top installation tool 302 includes an upper handle portion 303 and a lower, closure top engagement portion 304 configured to mate with and rotate the closure top 62.

The antitorque tool 300 is also preferably used with a closure top torquing tool 305, shown in FIGS. 47 and 48 . The tool 305 is used to torque and set the closure top 62, so it is snug against the rod 8, and thereafter break away the break-off head 186 in the manner shown in FIG. 48 . The torquing tool 305 is preferably in the form of a socket as shown in the drawings to allow for adequate tightening of the closure top 62 and also ease in removal of the break-off head 186 as shown in FIG. 48 .

The antitorque tool 300 includes a tubular hollow shaft 306 that is sized and shaped to be slidably received over the installation tool 302 and also the torquing tool 305. The shaft 306 has a lower end portion 308 that has a pair of diametrically spaced, curved bridges 310. Each of the bridges 310 is sized and shaped to fit over the rod 8, shown in FIGS. 47 and 48 . When in place, as illustrated in FIG. 47 , the antitorque tool 300 allows a surgeon to counter torque applied by the torquing tool 305, when applying torque to and breaking away the break-off head 186. The antitorque tool 300 also has an upper handle 316 disposed perpendicular to the shaft 306 and having an opening 318 through which the installation tool 302 and the torquing tool 305 passes in the manner suggested by FIGS. 46-48 .

In use, the previously described tools are utilized to attach one or more rods 8 to the human spinal column 6. The procedure is begun by selection of a bone screw 4 in accordance with the size of the patient's vertebra 16 and the requirements of the spinal support needed. Bone screws 4 having a rotatable or polyaxial head 146 are preferred but not required for the procedure, as such allow relatively easy adjustment of the rod 8 in the tools 9 and 10 during placement and for movement of the tools 9 and 10, as described below. The bone screw 4 is also preferably cannulated so as to be receivable over and guided by a guide pin 355 as discussed more fully below.

A relatively small incision, such as an incision 350 in the skin 20 is then made for each bone screw 4 to be used. Preferably, the incisions are sized so as to snugly receive the tools of the invention. The incisions 350 are stretched into a round shape with a circumference equal to or just slightly larger than the multi-purpose installation tool 12. The skin 20 is relatively flexible and allows the surgeon to move the incision 350 around relative to the spine 6 to manipulate the various tools and implants, as required. In some cases, two screws can be inserted through one or the same incision.

With reference to FIG. 36 , a drill (not shown) is utilized to form a first guide bore 366 in a vertebra 16 under guidance of non-invasive imaging techniques, which procedure is well known and established. The thin pin or guide wire 355 is then inserted in the first guide bore 366. This first guide bore 366 and associated thin pin 355 function to minimize stressing the vertebra 16 and provide an eventual guide for the placement and angle of the bone screw shank 148 with respect to the vertebra 16.

The guide bore 366 is enlarged utilizing a cannulated drilling tool or tap 360 having an integral or otherwise attached cannulated and threaded bit 362 with an outer surface sized and shaped to correspond to the size and shape of the chosen threaded bone screw 4. The drilling tool 360 cooperates with a cylindrical holder or sleeve 368 having an inner surface in slidable mating arrangement with the tool 360 and being held in a position substantially co-axial therewith. The holder 368 is sized and shaped to fit within the incision 350 and prevents soft tissues from being rolled up in the threaded bit 362 as it is rotated. The tool 360 further includes a handle 370 fixedly attached to the tool 360 located at an end portion 372 thereof and of a size and shape for rotating the bit 362 along the pin 355 and into the first bore 366.

With the pin 355 still in place, the enlargement of the guide bore 366 begins by threading the thin pin 355 through the end of the tap and inserting the holder 368 into the incision until the holder comes into contact with the vertebra 16. The drill bit 362 is advanced downward along the pin 355 until the drill bit 362 comes into contact with the vertebra 16. The tool 360 is then rotated within the holder 368 using the handle 370, driving the bit 362 along the pin 355 until a full sized bore 380 is drilled to a depth desired by the surgeon. During drilling, the holder 368 remains stationary, shielding the surrounding tissue from the rotational movement of the bit 362 and tool 360.

The tool 360 is then removed by rotating the bit 362 in reverse until the bit 362 is outside the bore 380. The tool 360 is then removed from the holder 368, followed by the removal of the holder 368 through the incision 350.

Before placing the bone screw 4 in the vertebra 16, the bone screw 4 is preferably joined to an associated guide tool 9 or 10, with or without an associated multi-purpose installation tool 12, and an associated driver 14. It is foreseen that the driver can also be cannulated. It is possible, but typically not desirable, to join a guide tool 9 or 10 to the bone screw 4 after the installation of the bone screw 4 to the vertebra 16. There also may be instances wherein it is desirable to join the bone screw 4 to an associated guide tool 9 or 10, but not to the multi-purpose installation tool support 12 or the driver 14 until after the bone screw 4 is installed in the vertebra 16, if at all. Furthermore, it is understood that the driver 14, cannulated or not, may be used with a guide tool 9 or 10 without the multi-purpose installation tool 12. However, it may be preferable to utilize the multi-purpose installation tool 12 during installation of a bone screw 4 into the vertebra 16 as the tool 12 provides some mechanical advantage and aids in preventing inadvertent splaying of side walls 32 and 33 of the end guide tool 9 and legs 102 and 103 of the intermediate guide tool 10.

The attachment structure 124 of the intermediate guide tool 10 is joined to a bone screw 4 by first rotating the tool 10 relative to the bone screw 4 so that the legs 102 and 103 are positioned as shown in FIGS. 17 and 18 , with the facets 167 and 177 of the head 146 disposed between the guide tool legs 102 and 103, and with the facet 167 adjacent the leg 102 and the facet 177 adjacent the leg 103, thereby aligning the groove 158 with the large pin 126 and the groove 168 with the large pin 130. A slight splaying of the legs 102 and 103 is possible during alignment with the head arms 150 and 151.

The head 146 is then twisted into place by rotating the tool 10 axially in a clockwise direction as shown by the arrow T in FIGS. 18 and 19 .

The twist-on procedure described herein with respect to the attachment structure 124 of the intermediate tool 10 is also followed with respect to the end guide tool 9 attachment structure 72. As previously stated herein, the attachment structure 72 is substantially similar to the attachment structure 124 of the intermediate tool 10, with the only difference being that the end guide tool 9 includes a flexible back wall tang portion 38 rather than the pass-through slot 111 of the intermediate guide tool 10.

After the bone screws 4 have been attached to the guide tools 9 and 10, a multi-purpose installation tool 12 can be attached to each of the guide tools 9 and 10. With respect to each of the intermediate guide tools 10, the multi-purpose installation tool 12 is preferably installed as follows: The rear wall 81 of the tool 10 is positioned adjacent to the surface 220 and the tool 10 is inserted into the hollow passage 206 and slid into the rod pusher sleeve 204 until the end 87 contacts the translation nut 210, with the block 218 preventing axial rotation of the guide tool 10 with respect to the multi-purpose installation tool 12, and resulting in the preferred alignment of the sleeve slot 11 and the opening 79 of the tool 10 with the U-shaped channel 212 of the multi-purpose installation tool 12. However, because the slot 11 is a pass-through slot, the alignment of the guide tool 10 with respect to the multi-purpose installation tool 12 is not critical to processes according to the invention. Therefore, in most instances the rear wall 81 of the tool 10 may also be positioned opposite the surface 220 upon entry into the multi-purpose installation tool 12.

The translation nut 202 is then rotated with the thread 228 of the nut 202 mating with the thread 93 of the tool 10. The nut 202 is rotated in a clockwise direction as illustrated by the arrow X in FIG. 29 until the end 87 is disposed outside of the nut 202 and positioned similar to what is shown with respect to the multi-purpose installation tool 12 and end guide tool 9 assembly shown in FIGS. 30 and 31 . The abutment pin 118 prevents further rotation of the nut 202 and advancement of the sleeve 204 beyond the pin 118.

As shown in FIGS. 29-31 , the end guide tools 9 are similarly equipped with multi-purpose installation tools 12. In order to compress the tang 38 during installation of a bone screw 4 into a vertebra 16, the tool 9 is received into the multi-purpose installation tool 12 with the back wall 28 of the tool 9 disposed adjacent to the surface 220. Then the multi-purpose installation tool 12 is slid onto the tool 9 until the end 43 contacts the translation nut 202, with the block 218 preventing axial rotation of the tool 9 with respect to the multi-purpose installation tool 12, and resulting in the preferred alignment wherein the flexible back wall tang portion or flap 38 is disposed adjacent to the guide tool sleeve 204 disposed opposite the U-shaped channel 212. The translation nut 202 is then rotated with the thread 228 of the nut 202 mating with the thread 50 of the end guide tool 9. The nut 202 is rotated in a clockwise direction as illustrated by the arrow X in FIG. 29 until the end 43 is disposed outside of the nut 202 and positioned as shown in FIGS. 30 and 31 , but not beyond the pin 67.

The driver 14 is then installed into the guide tool 9 as shown in FIGS. 32-35 and as follows: The driver 14 is first prepared for ease of insertion by placing the guide tool fastener 252 in the first or unattached position with the fastener 252 in contact with the annular surface 264 of the driver 14 as shown in FIG. 32 . Then, the driver end 256 is inserted into the guide tool 9 at the end 43 with the stem 254 being slid into the guide tool 9 with the pin 46 aligned with the channel 39 until coming to a stop with the pin 46 disposed in the slot 44 and the bone screw engager 256 in contact with the bone screw upper shank 154. A slight rotation or jiggling of the bone screw shank 148 may be required for the hex socket of the bone screw engager 256 to become positioned in operational engagement with the hex shaped upper shank 154. The guide tool fastener or nut 252 is then moved downward and toward the end 43 and then rotated clockwise as viewed from the handle 250 and illustrated by the arrow Y in FIG. 33 , mating the thread 50 disposed near the end 43 of the guide tool 9 with the inner threaded surface 262 of the nut 252 of the driver 14. The nut 252 is rotated in this clock-wise fashion and hand-tightened until further translation of the nut 252 along the guide tool 9 is prevented by the pin 266 abutting the upper seating surface 272.

If, after the fastener 252 is rotated to a hand-tightened position, and a gap or space remains between the fastener 252 and the translation nut 202 as shown in FIG. 33 , the translation nut 202 is rotated counter-clockwise as shown by the arrow Z in FIG. 33 , and hand-tightened until the translation nut 202 abuts against the fastener 252 as shown in FIG. 34 . The assembly 1 is now ready for bone screw installation into the vertebra 16.

The driver 14 is installed into the intermediate guide tool 10 and multi-purpose installation tool 12 assembly in steps similar to that described above with respect to the end guide tool 9.

A series of bone screws 4 are installed in each vertebra 16 to be attached to the rod 8 by inserting each of the assemblies 1 through the skin incision 350 as shown in FIG. 37 . The screw 4 is then rotated and driven into the tapped bore 380 with the surgeon holding and rotating the assembly 1 with the driver handle 250, thereby rotating the entire assembly 1 as one unit until the shank 148 is disposed at a desired depth in the tapped bore 380 of the respective vertebra 16. Preferably, the shank 148, along with the screw driver 14 are also cannulated to receive the pin 355, providing additional guidance for installation of the bone screw 4 into the vertebra 16.

After a specific bone screw 4 is installed, the driver 14 is removed from either the guide tool 9 or 10 by rotating the fastener 252 in a counter-clockwise direction (illustrated by the arrow Z in FIG. 33 ) and sliding the shaft 254 towards the open end 230 of the multi-purpose installation tool 12, if used, and pulling the driver 14 out of the assembly 1 by the handle 250.

With respect to the end guide tools 9, the multi-purpose installation tool 12, if used, is then removed by rotating the translation nut 202 counter-clockwise until the thread 228 disposed on the inner surface 224 of the translation nut 202 is disengaged from the thread 50 of the tool 9. The multi-purpose installation tool 12 is then slid off of the tool 9 deploying the flexible flap 38, as shown in FIG. 38 . If desired at this junction of a process according to the invention, the multi-purpose installation tool 12 many then be rotated 180 degrees and replaced on the tool 9 with the slot 44 and the channel openings 40 and 94 aligned adjacent to and facing the alignment block 218 of the multi-purpose installation tool 12 for a rod pushing application. The translation nut 202 is then rotated clockwise as illustrated by the arrow X in FIG. 29 . In this rod pushing position, the flexible tang 38 is extendible into the U-shaped channel 212 of the multi-purpose installation tool 12.

For each bone screw 4, an associated guide tool 9 or 10 extends through the skin 14, as illustrated in FIG. 39 . An end guide tool 9 is located at each end of the series of bone screws 4 and an intermediate guide tool 10 is located on each intermediate bone screw 4.

In order to install a rod 8 in two or more bone screws 4, it may not be necessary to equip each guide tool 9 or 10 with a multi-purpose installation tool 12. For example, with reference to FIG. 40 , for a particular procedure, it may be desirable to utilize only one multi-purpose installation tool 12 with a tool set 2 according to the invention. In the process illustrated by the FIG. 40 , the multi-purpose installation tools 12 have been removed from both of the end guide tools 9 and both of the intermediate guide tools 10 after which a rod 8 has been inserted and a multi-purpose tool 12 reattached to one tool 10. Some pushing of the rod may be accomplished by just extending a rod or tool down the central channel of the guide tools 9 and 10 when mechanical advantage is not required to move the rod 8. As required by the surgeon, one or more multi-purpose installation tools 12 may be added or removed at any time during the course of the rod pushing or reducing procedure.

With reference to FIG. 39 , prior to installation of the rod 8, the end guide tools 9 are turned or rotated so the channels 55 therein face one another and the intermediate guide tools 10 are aligned so the pass-through slots 111 align with the channels 55.

With reference to FIG. 40 , the rod 8 has been inserted diagonally through one of the end skin incisions 350 with the adjacent end guide 9 pushed to the side, so that one of the rod ends 59 first passes through the slots 111 in the intermediate guide tools 10 and then into the channel 55 of one of the guide tools 9. Back muscle tissue separates easily here to allow the upper insertion of the rod 8 and can be further separated by finger separation or cutting through one of the incisions 350, if required.

After initial insertion, the remaining opposed end 59 of the rod 8 is positioned in the channel 55 of the end guide tool 9 that is located next to the insertion point of the rod 8. Manipulation of the rod 8 in the channels 55 is aided by the back wall tang portions or flexible flaps 38 of the guide tools 9 which may also be moved like a joy-stick toward or away from each other by the surgeon. Furthermore, once the rod 8 is disposed within the channels 111 and 55, the back wall portions or flaps 38 resiliently bias against the rod ends 59, substantially holding and containing the rod 8 in place between the end guide tools 9 of the tool set 2. The reason that the tangs 38 are needed is that the rod 8 extends beyond the end bone screws 4 and the end guide tool 9 are located on the end bone screws 4. Also, the rod may tend to slip out of one end screw head. When the rod is spaced above the bone screws 4, the guide tools 9 can be manipulated to be spaced farther apart to receive the rod 8 therebetween, but as the rod 8 nears the bone screws 4, the guide tools 9 cannot be manipulated enough to compensate so the rod 8 must extend beyond the bodies of the guide tool 9. Therefore, the tangs 38 allow the rod 8 to be controlled and positioned outwardly of the end bone screws 8. Moreover, the position of the rod 8 is controlled by equal pressure applied by the tangs 38 so that the rod 8 extends past the bone screws 4 approximately an equal amount on each side.

Also with reference to FIGS. 40 and 41 , once the rod 8 is positioned in the guide tools 9 and 10, the multi-purpose installation tool 12 may be utilized to push the rod 8 toward the bone screw 4, normally when mechanical advantage is needed to seat the rod 8 in the bone screws 4. This is accomplished by rotating the translation nut 202 in a clockwise direction (as viewed from above the skin 20), thereby translating the sleeve 204 in a downward direction toward the bone screw 4, with the guide tool alignment block 218 abutting and pushing against the rod 8. It is also possible to reduce or realign vertebral bodies by this maneuver.

As shown in FIG. 40 , it may also be desirable to simultaneously or thereafter push the rod 8 toward the screw 4 of one or more guide tools 9 and 10 utilizing the closure top installation tool 302 pushing against a closure top 62 that in turn pushes against the rod 8. In particular, a closure top 62 is placed in the elongate top to bottom channel associated with the guide tools 9 and 10, preferably by entry from the side such as into the channel opening 40 of the guide tool 9 or alternatively into the channel 39 through the top end 43 of the guide tool 9. If the guide tool 9 or 10 has the multi-purpose installation tool 12 attached, the closure top 62 can be placed into the guide tool by side insertion into the U-shaped channel 212. The closure top installation tool 302 is then inserted into the top end 43 and through the channels disposed within the guide tool 9, until the engagement portion 304 mates with a cooperating aperture disposed in the break-off head 186. The closure top 62 is then driven or pushed under manual control of the surgeon by use of the installation tool 145 toward the rod 4.

With reference to FIG. 42 , near the bottom of the guide tools 9 and 10, such as near the end 112 of the intermediate tool 10 and the bottom 36 of the back wall 28 of end guide tool 9, the closure top 62 engages the helically wound guide and advancement structures 64 and 114 of respective guide tools 9 and 10. The tools 302 and mated closure tops 62 are then rotated, mating the closure tops 62 with associated guide tools 9 and 10 so as to drive the closure top 62 downward against the rod 8 and to urge the rod 8 downward into the bone screw channel 153. Preferably, the translation nut 202 of the multi-purpose installation tool 12 is rotated in a clockwise direction, translating the sleeve 204 and block 218 downwardly slightly in advance or substantially concurrent with the advancement of the closure tops 62, providing additional mechanical advantage for the block flat surface 222 against the rod 8.

With reference to FIG. 43 , at the bottom of the guide tool 9 or 10, the closure top mating structure 181 engages and begins to mate with the guide and advancement structure 183 on the respective bone screw 4 and continued rotation of the tool 302 drives the rod 8 downward and into engagement with the upper part of the bone screw shank 154, so as to snug against and frictionally lock the shank 148 in position relative to the bone screw head 146.

Once all of the closure tops 62 are in final seated position in respective bone screws 4 and the surgeon is satisfied with the position of all of the elements, such as is illustrated in FIG. 43 , any and all multi-purpose installation tools 12 are removed by rotating the nut 202 counter-clockwise followed by sliding the sleeve 204 off of the guide tool 9 and 10 and out of the incision 350. Thereafter, each of the guide tools 9 and 10 are now removed by rotating each guide tools 9 and 10 ninety degrees so that the recesses 116 straddle the rod 8 to allow the attachment structure 72 or 124 to disengage from the receiver portion 145 on the bone screw 4. The guide tool 9 or 10 is then pulled axially upward away from the bone screw 4, along the tool 302 and then out of the incision 350.

The antitorque tool 300 is mounted over each closure top installation tool 302, utilizing the tool 302 as a guide for re-entry through the incision 350. The antitorque tool 300 is slid along the tool 302 until the bridges 310 straddle the rod 8, preventing axial rotation of the tool 300. As shown in FIG. 46 , the closure top installation tool 302 is then pulled axially upward away from the bone screw 4 and out of the incision 350.

With reference to FIG. 47 , the closure top torquing tool 305 is then inserted into the antitorque tool 300 and engaged with the break-off head 186. By cooperative use of the tools 300 and 305 a preselected torque is manually applied to the break-off head 186 which breaks from the closure top 62 as illustrated in FIG. 48 and is thereafter removed, followed by removal of the antitorque tool 300, after which the incision 165 is closed.

With reference to FIGS. 49-53 , an alternative attachment structure, generally 401, is illustrated. A portion of the structure 401 is located on a polyaxial bone screw head or receiver 406 that is pivotally attached to a shank 407. Shown in phantom in the illustrated embodiment, the threaded shank 407 is cannulated, having a small central bore 408 extending an entire length of the shank body. The bore 408 provides a passage through the shank interior for a length of wire or pin inserted into a vertebra prior to the insertion of the threaded shank body 407, the wire or pin providing a guide for insertion of the shank 407 into the vertebra.

The attachment structure 401 for holding cooperation between the polyaxial bone screw head or receiver 406 and a guide tool 410 is also located at a lower end portion 411 of the guide tool 410. The lower end portion 411 has a cutout 412 and an inner attachment ledge 413. The attachment ledge 413 has a body 414 with an upperwardly extending, projection, flange or hook member 415 that follows an inner curvature of the guide tool 410. The body 414 extends radially inwardly and is sized and shaped to mate with and set within a tool receiving recess or groove 418 formed on the bone screw head 406. The recess 418 is sufficiently wide to simultaneously receive both the body 414 and the hook member 415 in a radially inward direction, as is shown in FIG. 52 . The attachment 413 is then set by axially raising the guide tool 410 relative to the bone screw 406 so at least part of the hook member 415 is located in an upper hidden recess 420, thereby securing the guide tool 410 to a respective bone screw 406, as shown in FIG. 53 . This locks the guide tool 410 to a respective bone screw 406 and prevents outward splaying of the guide tool 410. This is a snap-on type installation or assembly as seen in FIG. 49 where the leg 411 splays outward during initial placement of the guide tool 410 over the bone screw 406 and then returns to an unsplayed position when the inner attachment structure 413 seats in the receiving recess 418, as shown in FIG. 52 .

Alternatively, the guide tool 410 can be rotated approximately 90 degree. about a rotational axis thereof prior to joining with a respective bone screw 406, the attachment structure 413 lowered through the opening between bone screw arms 424 and 425 and aligned with the tool receiving recess 418, after which the guide tool 410 is rotated back to the first position shown in FIG. 53 in a twist on type assembly. In some instances the guide tool 410 is rotated somewhat more or less than ninety degrees to make the necessary alignment for removal which depends on the specific construction of the parts.

To remove the guide tool 410 from the bone screw receiver 406, the guide tool 410 is rotated ninety degrees to align the inner attachment ledge 413 with the opening between bone screw arms 424 and 425, to allow the attachment structure 413 to disengage from the recess 418. The guide tool 410 is then pulled axially upward away from the bone screw 406.

With reference to FIGS. 54-56 , a second alternative attachment structure, generally 430, for holding attachment of a bone attachment structure and a guide tool is illustrated. A polyaxial bone screw head or receiver 434 with a pivotally attached bone screw shank 435 is shown cooperating with a guide tool 436 having a lower end portion 438 thereof. On the bone screw receiver 434, the attachment structure 430 includes tool engaging apertures 440 formed on outer surfaces of arms 444 and 445 for holding the receiver 434 during procedures such as bone screw assembly, implantation of the shank 435 into a vertebra, and subsequent procedures, such as rod reduction and closure top installation. The illustrated apertures 440 are substantially circular in cross-section and are disposed opposite one another, each including an upwardly projecting, hidden inner recess 448 for cooperating with complimentary bone screw holding components of the guide tool 436, discussed more fully below. It is noted that the apertures 440 and the cooperating guide tool holding components may be configured to be of a variety of sizes and locations for attachment to the guide tool along any of the surfaces of the arms 444 and 445.

On the guide tool 436, the attachment structure 430 is disposed at the lower portion 438 and on inner slightly recessed surfaces 452 and 453 of respective legs or surfaces 456 and 457. The attachment structure 430 includes diametrically opposed projections or pins 460 and 462, extending radially inwardly from the surfaces 452 and 453, respectively. The pins 460 and 462 are substantially configured the same, both being substantially rounded, radially inward projecting nodules, each having a lip 464 projecting upwardly and away from a bottom surface 468 and 469, respectively. Each lip 464 partially defines a groove 470 for receiving the bone screw receiver 434. The groove 470 is further defined by a base surface 472 and a wall 474 that faces the inner surface 452 or 453. An upper wall 476 is substantially parallel to the base or bottom surface 468 or 469.

The pins 460 and 462 are configured to mate with the opposed apertures 440 of the bone screw head or receiver 434 with the lip 464 extending into the inner recess 448, when the guide tool 436 is fully installed on the bone screw head 434 as shown in FIG. 56 and described more fully below. While a preferred embodiment of the invention has pins 460 and 462 of the implant engaging structure 430 on the guide tool 436, and apertures 440 on the bone screw head 434, it is foreseen that these elements could be reversed in total or part in accordance with the invention.

In use, before implanting the bone screw shank 435 in a vertebra, the bone screw head or receiver 434 is preferably joined to the guide tool 436. It is also possible to join the guide tool 436 to the bone screw receiver 434 after the installation of the bone screw to the vertebra. The cooperating implant engaging structure 430 disposed on the guide tool 436 and the head or receiver 434 is joined by first manually spreading the legs 456 and 457 apart and inserting the guide tool 436 onto the bone screw head 434 as illustrated in FIG. 54 . The inwardly projecting pins 460 and 462 are generally aligned with the apertures 440 and the tool is slid downwardly along the head 434 surface until the pins 460 and 462 snap into the apertures 440 as shown in FIG. 55 . With reference to FIG. 56 , the guide tool 435 is then pulled upwardly and away from the bone screw head 434, causing the lips 464 to enter the recesses 448. Engagement between the lips 464 and the structure defining the recesses 448 result in a firm attachment that also resists any attempt to spread or splay the legs 456 and 457.

To remove the guide tool 436 from the bone screw head 434, downward force is first placed on the guide tool 436 by the surgeon to move the lips 464 of the guide tool implant engaging structure 430 out of the inner recesses 448 of the bone screw head 434. Then a prying tool may be inserted between the legs 456 and 457 to spread the lower portions of the legs 456 and 457 away from one another, while pulling up on the guide tool 436 to allow the guide tool to slide upwardly along the bone screw head 434 (as illustrated in reverse by FIGS. 56, 55 and 54 ). The guide tool 436 is then pulled axially upwardly away from the bone screw head 434.

With reference to FIGS. 57-59 , a third alternative attachment structure, generally 480, for holding a bone attachment, such as the bone screw, generally 482, to a guide or holding tool 484 is illustrated. The illustrated bone screw 482 includes a head or receiver 486 hingedly attached to a bone screw shank 487. With reference to FIG. 57 , the shank 487 is bottom loaded into the receiver 486 and then rotated ninety degrees to seat an upper portion 489 of the shank 487 within the receiver 486 as shown in FIG. 59 . First and second arms 490 and 492 of the receiver 486 each include outer substantially planar surfaces 494. Each outer surface 494 of each arm 490 and 492 also includes a substantially V-shaped undercut 496 disposed near and running parallel to a top surface 498, the undercut 496 extending along and through end surfaces 497 of the receiver 486 and sized and shaped for cooperating with complimentary bone screw holding components of the guide tool 484. The undercut 496 includes a planar surface 500 disposed at an acute angle with respect to a second surface 501, the surface 501 being perpendicular to the top surface 498.

On the guide tool 484, the attachment structure 480 includes diametrically opposed projections in the form of straight, hook-like ledges 502 extending along inner surfaces of the tool 484 and projecting inwardly and upwardly (operably in a direction away from the bone screw 482 and toward a remainder of the tool 484). The hook-like ledges 502 are sized and shaped to be received in the undercut 496 and be in frictional engagement with the angled surfaces 500. First and second set screws 504 rotatably attached to the guide tool 484 are sized and shaped for frictional engagement with the top surface 498 of the receiver arms 490 and 492, respectively, thereby frictionally fixing the projecting ledges 502 within the undercut 496.

In use, before implanting the bone screw shank 487 in a vertebra, the bone screw head or receiver 486 is preferably joined to the guide tool 484. It is also possible to join the guide tool 484 to the bone screw receiver 486 after the installation of the bone screw to the vertebra. The cooperating implant engaging structure 480 disposed on the guide tool 484 and the head or receiver 486 may be joined in more than one way. One option is to manually spread opposed legs or portions 506 and insert the guide tool 484 onto the bone screw receiver 486 outer arm surface 494 at a location spaced from the top surfaces 498, thereby snapping the guide tool 484 onto the receiver 486 and thereafter pulling the guide tool 484 upwardly and away from the receiver 486, the guide tool 484 sliding upwardly along an inwardly sloping surface 507 leading up to the undercut 496 until the ledges 502 are received in the undercut 496. Engagement between the ledges 502 and the sloped surfaces 500 result in a firm attachment that also resists any attempt to spread or splay the legs 506. The set screws 504 may then be rotated and thereby moved into frictional engagement with the top surfaces 498.

Alternatively, the implant engaging structure 480 on the guide tool 484 may be aligned with the undercut 496 on the receiver 486, the tool 484 disposed laterally of the bone screw receiver 486. Then the tool 484 may be slid onto the bone screw receiver 486 with the ledges 502 in sliding engagement in the surfaces 500 of the undercuts 496 until the ledges 502 are fully received in the undercuts 496. To fully engage the ledges 502 with the surfaces 500, the guide tool 484 is pulled upwardly and away from the receiver 486. The set screws 504 may then be rotated and placed in frictional engagement with the top surfaces 498.

To remove the guide tool 484 from the bone screw head 434, the set screws 504 are first rotated until the screws 504 are spaced from the top surfaces 498. Downward force is then placed on the guide tool 484 by the surgeon to move the ledges 502 of the guide tool implant engaging structure 480 slightly out of the undercut 496. Then the guide tool 484 is slid in a lateral direction, out of the undercut 496.

It is to be understood that while certain forms of the present invention have been illustrated and described herein, it is not to be limited to the specific forms or arrangement of parts described and shown. For example, it is foreseen that more than one tool could be used to provide the described functions for the multi-purpose installation tool 12. It is also possible to use the invention in an open surgical wound. Different types of screw drivers, both cannulated and non-cannulated, can be used with the invention. 

What is claimed is:
 1. A method of implanting a rod along a human spine by attaching the rod to individual vertebrae in a selected group of vertebrae, the method comprising the steps of: a) forming an incision in a patient's skin generally above at least two of the selected vertebrae; b) inserting a polyaxial bone screw through each incision and implanting the bone screw in a respective vertebra; c) joining an end guide tool to each of a pair of end bone screws to be used in conjunction with a pair of vertebrae at opposite ends of the selected group of vertebrae; wherein each of the end guide tools is provided with an elongate channel extending from a bottom of a respective end guide tool to a top thereof that is sized and shaped to receive an end of the rod; wherein each of the end guide tools includes an elongated body including a proximal handle portion and a distal engaging portion configured to releasably engage the bone screw, the distal engaging portion including a first leg and a second leg opposing each other, each of the first and second legs including an inner surface and a first engagement pin extending radially inward from the inner surface near a distal end thereof, and the first engagement pin is configured to mate with a first groove at a head of the bone screw via twisting the elongated body relative to the head of the bone screw, the first groove extending along a direction perpendicular to a proximal-distal direction of the elongated body, so at least part of the inner surface is separated from an outer surface of the head of the bone screw when the tool is installed on the bone screw; d) rotating the end guide tools such that the channels are facing each other; e) inserting the rod through one of the incisions so that each of the rod ends engages a respective channel; f) urging the rod along the channels to a bottom of the end guide tools and into heads of respective bone screw; and g) guiding a closure insertion tool into the elongate channel by one of an axial loading pathway and a sideways loading pathway and thereafter utilizing the insertion tool to insert a closure into a respective bone screw.
 2. The method according to claim 1 including the steps of: providing an intermediate guide tool for each bone screw used with each vertebra of the selected group of the vertebrae between the end vertebrae wherein each the intermediate guide tool has an elongate slot extending upward from a bottom of the intermediate guide tool; and inserting the rod through each of the slots when placing the rod in the channels such that the rod is guided by the slots to respective bone screws.
 3. The method according to claim 1, wherein each of the end guide tools further includes a lip at or near an inner end of the first engagement pin extends proximally from the first engagement pin thereby defining a slot between the inner surface and the lip.
 4. The method according to claim 1, wherein the first engagement pin is disposed adjacent a rod- abutment recess extending from a first side surface of each of the first and second legs toward the first engagement pin.
 5. The method according to claim 4, wherein the rod-abutment recess is configured to allow twisting of the tool and freeing of the distal engagement portion from the bone screw when a spinal rod is placed in the head of the bone screw.
 6. The method according to claim 1, wherein the first engagement pin of the first leg and the first engagement pin of the second leg are disposed in a diametrically opposed relation to each other.
 7. The method according to claim 1, The tool of claim 1, wherein the first engagement pin is configured to mate with the first groove at the head of the bone screw without splaying of the first and second legs.
 8. The method according to claim 1, wherein each of the first and second legs include a second engagement pin extending radially inward from the inner surface near the distal end thereof, wherein the second engagement pin is configured to mate with a second groove at the head of the bone screw via twisting the elongated_body relative to the head of the bone screw.
 9. The method according to claim 8, wherein the second engagement pin is of a different size from the first engagement pin.
 10. The method according to claim 8, wherein the second engagement pin of the first leg is configured to mate with a second groove at the head of the bone screw with a transition from splaying of the first leg to a non-splaying configuration of the first leg.
 11. A method of inserting a spinal rod into a pair of end bone screws comprising the steps of: a) providing a pair of end guide tools with each end guide tool having a side facing and rod receiving channel extending along the entire length thereof; wherein each of the pair of end guide tools includes an elongated body including a proximal handle portion and a distal engaging portion configured to releasably engage the bone screw, the distal engaging portion including a first leg and a second leg opposing each other, each of the first and second legs including an inner surface and a first engagement pin extending radially inward from the inner surface near a distal end thereof, and the first engagement pin is configured to mate with a first groove at a head of the bone screw via twisting the elongated body relative to the head of the bone screw, the first groove extending along a direction perpendicular to a proximal-distal direction of the elongated body, so at least part of the inner surface is separated from an outer surface of the head of the bone screw when the tool is installed on the bone screw; b) inserting the guide tool through a patient's skin and in communication with each respective end bone screw; c) inserting a rod and directing opposite ends of the rod into the channels; d) guiding the rod ends in the channels to the bone screws; and e) guiding a closure insertion tool with a closure thereon along a respective channel from near a top thereof to a respective bone screw and thereafter inserting the closure into the bone screw.
 12. The method according to claim 11, including the steps of: providing an intermediate guide tool for each bone screw used with each vertebra of the selected group of the vertebrae between the end vertebrae wherein each the intermediate guide tool has an elongate slot extending upward from a bottom of the intermediate guide tool; and inserting the rod through each of the slots when placing the rod in the channels such that the rod is guided by the slots to respective bone screws.
 13. The method according to claim 12 including the steps of: attaching the guide tool to the bone screw before inserting the bone screw in the vertebra; prior to inserting the rod, inserting a driver through a lengthwise extending sideways opening channel in the guide tool and using the driver to install the bone screw in the vertebra; and thereafter removing the driver from the guide tool.
 14. The method according to claim 12, wherein the tool further includes a lip at or near an inner end of the first engagement pin extends proximally from the first engagement pin thereby defining a slot between the inner surface and the lip.
 15. The method according to claim 12, wherein the first engagement pin is disposed_(—) adjacent a rod-abutment recess extending from a first side surface of each of the first and second legs toward the first engagement pin.
 16. The method according to claim 15, wherein the rod-abutment recess is configured to allow twisting of the tool and freeing of the distal engagement portion from the bone screw when a spinal rod is placed in the head of the bone screw.
 17. The method according to claim 12, wherein the first engagement pin of the first leg and the first engagement pin of the second leg are disposed in a diametrically opposed relation to each other.
 18. The method according to claim 12, The tool of claim 1, wherein the first engagement pin is configured to mate with the first groove at the head of the bone screw without splaying of the first and second legs.
 19. The method according to claim 12, wherein each of the first and second legs include a second engagement pin extending radially inward from the inner surface near the distal end thereof, wherein the second engagement pin is configured to mate with a second groove at the head of the bone screw via twisting the elongated body relative to the head of the bone screw.
 20. The method according to claim 12, wherein the second engagement pin of the first leg is configured to mate with a second groove at the head of the bone screw with a transition from splaying of the first leg to a non-splaying configuration of the first leg. 